BARLEY GROWERS must learn from what happened in wheat to prevent fungicide resistance developing, says Syngenta”s field technical manager Chris Rowsell. “There”s no reason to suggest the same things couldn”t happen in barley.”

A tiny proportion of net blotch spores have been found to have a partial resistance to strobilurins, admits the firm”s head of disease control Dietrich Hermann. “It”s a different mutation [to septoria], but no field performance issues have been reported yet.”

As with septoria, rhynchosporium spores have also been shown to be less sensitive to triazole. Trials data suggests using two triazole sprays in a season could exacerbate the problem, he says. “Those data are a little bit frightening.”

Growers must protect both fungicide groups by adopting a mixed chemistry approach, says Mr Rowsell. “For the most part they are already doing that, but using triazoles only once in the programme at T2 may help prolong triazole life.”